Consolidate white_label to remove_branding and add embed widget

- Rename white_label feature to remove_branding across frontend/backend
- Update billing catalog, plan features, and permission checks
- Add dark mode support to Recharts tooltips with useDarkMode hook
- Create embeddable booking widget with EmbedBooking page
- Add EmbedWidgetSettings for generating embed code
- Fix Appearance settings page permission check
- Update test files for new feature naming
- Add notes field to User model

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/components/__tests__/UpgradePrompt.test.tsx

@@ -68,7 +68,7 @@ describe('UpgradePrompt', () => {
     });
 
     it('should render for any feature in inline mode', () => {
-      const features: FeatureKey[] = ['plugins', 'custom_domain', 'white_label'];
+      const features: FeatureKey[] = ['plugins', 'custom_domain', 'remove_branding'];
 
       features.forEach((feature) => {
         const { unmount } = renderWithRouter(
@@ -140,7 +140,7 @@ describe('UpgradePrompt', () => {
         'webhooks',
         'api_access',
         'custom_domain',
-        'white_label',
+        'remove_branding',
         'plugins',
       ];
 
@@ -243,7 +243,7 @@ describe('UpgradePrompt', () => {
 
     it('should make children non-interactive', () => {
       renderWithRouter(
-        <UpgradePrompt feature="white_label" variant="overlay">
+        <UpgradePrompt feature="remove_branding" variant="overlay">
           <button data-testid="locked-button">Click Me</button>
         </UpgradePrompt>
       );
@@ -374,7 +374,7 @@ describe('LockedSection', () => {
   describe('Different Features', () => {
     it('should work with different feature keys', () => {
       const features: FeatureKey[] = [
-        'white_label',
+        'remove_branding',
         'custom_oauth',
         'can_create_plugins',
         'tasks',
@@ -470,7 +470,7 @@ describe('LockedButton', () => {
       const handleClick = vi.fn();
       renderWithRouter(
         <LockedButton
-          feature="white_label"
+          feature="remove_branding"
           isLocked={true}
           onClick={handleClick}
         >